Polyethylene solubility parameter

There are thus no solvents at room temperature for polyethylene, polypropylene, poly-4 methylpent-l-ene, polyacetals and polytetrafluoroethylene. However, as the temperature is raised and approaches F , the FAS term becomes greater than AH and appropriate solvents become effective. Swelling will, however, occur in the amorphous zones of the polymer in the presence of solvents of similar solubility parameter, even at temperatures well below T. ... 

In the case of crystalline polymers better results are obtained using an amorphous density which can be extrapolated from data above the melting point, or from other sources. In the case of polyethylene the apparent amorphous density is in the range 0.84-0.86 at 25°C. This gives a calculated value of about 8.1 for the solubility parameter which is still slightly higher than observed values obtained by swelling experiments. 

Hence polyethylene will be more permeable to liquids of similar solubility parameter, e.g. hydrocarbons, than to liquids of different solubility parameter but of similar size. The permeabilities of a number of polymers to a number of gases are given the Table 5.77. ... 

Since polyethylene is a crystalline hydrocarbon polymer incapable of specific interaction and with a melting point of about 100°C, there are no solvents at room temperature. Low-density polymers will dissolve in benzene at about 60°C but the more crystalline high-density polymers only dissolve at temperatures some 20-30°C higher. Materials of similar solubility parameter and low molecular weight will, however, cause swelling, the more so in low-density polymers Table 10.5). 

Being a hydrocarbon with a solubility parameter of 18.6MPa - it is dissolved by a number of hydrocarbons with similar solubility parameters, such as benzene and toluene. The presence of a benzene ring results in polystyrene having greater reactivity than polyethylene. Characteristic reactions of a phenyl group such as chlorination, hydrogenation, nitration and sulphonation can all be performed with... 

The principal polyolefins are low-density polyethylene (ldpe), high-density polyethylene (hope), linear low-density polyethylene (lldpe), polypropylene (PP), polyisobutylene (PIB), poly-1-butene (PB), copolymers of ethylene and propylene (EP), and proprietary copolymers of ethylene and alpha olefins. Since all these polymers are aliphatic hydrocarbons, the amorphous polymers are soluble in aliphatic hydrocarbon solvents with similar solubility parameters. Like other alkanes, they are resistant to attack by most ionic and most polar chemicals their usual reactions are limited to combustion, chemical oxidation, chlorination, nitration, and free-radical reactions. 

When heated. PP dissolves in nonpolar solvents with solubility parameters in the range of 6.5 to 9.5 H, but it is resistant to polar solvents, such as ethanol. PP is more resistant to environmental stress cracking than polyethylene. 

Solubility parameters of 19.3,16.2, and 16.2 (f/cm3)1 2 (7.9 (cal/cm3)1 2) have been determined for polyoxetane, poly(3,3-dimethyloxetane), and poly(3,3-diethyloxetane), respectively, by measuring solution viscosities (302). Heat capacities have been determined for POX and compared to those of other polyethers and polyethylene (303,304). The thermal decomposition behavior of poly[3,3-bis(ethoxymethyl)oxetane] has been examined (305). 

Most carriers are aromatic compounds, and have similar solubility parameters to the polyethylene tcrephthalate) libers and to some disperse dyes. 

Many computational studies of the permeation of small gas molecules through polymers have appeared, which were designed to analyze, on an atomic scale, diffusion mechanisms or to calculate the diffusion coefficient and the solubility parameters. Most of these studies have dealt with flexible polymer chains of relatively simple structure such as polyethylene, polypropylene, and poly-(isobutylene) [49,50,51,52,53], There are, however, a few reports on polymers consisting of stiff chains. For example, Mooney and MacElroy [54] studied the diffusion of small molecules in semicrystalline aromatic polymers and Cuthbert et al. [55] have calculated the Henry s law constant for a number of small molecules in polystyrene and studied the effect of box size on the calculated Henry s law constants. Most of these reports are limited to the calculation of solubility coefficients at a single temperature and in the zero-pressure limit. However, there are few reports on the calculation of solubilities at higher pressures, for example the reports by de Pablo et al. [56] on the calculation of solubilities of alkanes in polyethylene, by Abu-Shargh [53] on the calculation of solubility of propene in polypropylene, and by Lim et al. [47] on the sorption of methane and carbon dioxide in amorphous polyetherimide. In the former two cases, the authors have used Gibbs ensemble Monte Carlo method [41,57] to do the calculations, and in the latter case, the authors have used an equation-of-state method to describe the gas phase. 

Highly crystalline polymers such as polyethylene and poly(tetrafluoroethylene) are insoluble in all solvents at room temperature. These polymers, however, obey the solubility parameters rules at T > 0.9Tm. For instance, polyethylene becomes soluble above 80 °C. 

Galin, M., "Gas-Liquid Chromatography Study of Polyethylene oxide)- Solvent Interactions Estimation of Polymer Solubility Parameter," Polymer, 24, 865 (1983). 

It should be pointed out that in both these cases the degree of chlorination differs from PVC by around 10%. By any estimate, the heat of mixing in these cases should be quite unfavourable. For example, an estimate based on solubility parameters and using group contribution gives for PVC (6 = 19.28 J cm ) and chlorinated polyethylene (45wt.-%Cl) (5 = 18.77 J cm" ), hence for a 50/50 mixture AH is -1-0.065 J per cm of mixture. Together with unfavourable equation-of-state terms and a small combinatorial entropy contribution these mixtures would not be expected to be miscible. 

Sakellariou, P. Rowe, R.C. White, E.T.F. The solubility parameters of some cellulose derivatives and polyethylene glycols used in tablet film coating. Int. J.Pharm. 1986, 57, 175-177. 

For some applications, polymers are blended to provide a balance of properties. Some polymers blend well due to mutual solubility, but if the solubility parameter of the candidate polymers is different by more than about 3 SI units, the polymers must be blended with an intermediate material to improve compatibility. Typically, this involves an intermediate polymer with a low molecular weight. In the melt, this serves to reduce the surface tension between two incompatible polymers, thus improving dispersion. Low molecular weight polyethylene is an example of a polymer blending aid. In other cases, metal stearates or salts can be used to aid dispersion. Examples include zinc stearate and calcium stearate. 

Qualitatively MTBE Is estimated to have an overall solubility parameter value close to that of Indolene, but has higher polar and hydrogen bonding forces. As a result polar polymers such aa fluorocarbon, epichlorohydrin homopolymer and chlorosulfonated polyethylene tend to swell to a greater extent In MTBE rich mixtures, while nonpolar EPDM elastomer swells to a lesser extent In these mixtures. The very large swell of the fluorocarbon In MTBE Is not surprising since other ethers such as diethyl ether and dioxane are known to swell the fluorocarbon to a large extent [3]. 

Considering Table 1.16, only the first polymer, polyethylene, has non-polar contributions alone the next three have also polar components and the last, nylon-6,6, has contributions from all three forces. The largest solubility parameter for this polymer also corresponds to the highest melting point and stiffness, reflecting the importance of cohesive energy density as a measure of intermolecular forces. 

Cernia, E. M., and C. Mancini. 1965. A new method for determination of the solubility parameters of the polyethylene-ethylene pair at high temperature and pressure. Polym. Letters 3 1093. 

Blending within the family of PO has, however, been more common [Plochocki, 1978]. Although they are usually immiscible with each other, there exists some degree of mutual compatibihty between them. The similarity of their hydrocarbon backbones and the closeness of their solubility parameters, although not adequate for miscibility, accounts for a relatively low degree of interfacial tension. Eor example, the solubility parameters of polyethylene, polyisobutylene, ethylene-propylene rubber and polypropylene are estimated to be 16.0, 15.4,... 

There have been extensive applications of isotactic polypropylene (iPP)/EPM blends. These were used to produce rubber toughened polypropylene blends and subsequently polyolefin thermoplastic elastomers (88,89). Most commercial EPMs contain more than 50 mol% of ethylene, and these are elastomers. The solubility parameter of EPM should be intermediate to those of polyethylene and polypropylene dependent on ethylene content. Thus, it is often used to compatibilize PE/PP blends (90,91). 

Distribution of fibers Aspect ratio Filler Frequency of oscillation Coefficient of expansion of filler Shear modulus Gibbs free energy Heat of reaction, change Hildebrand unit, solubility parameter value High-density (linear) polyethylene Heat deflection temperature... 

Complications such as these extend also to the case of polytetra-fluoroethylene. The large difference in estimated solid-vacuum tensions between this polymer and polyethylene is not imexpected, since a proportionately large difference exists for the liquid surface tensions of hydrocarbons and fluorocarbons having five to eight carbon atoms [58]. The underlying cause of this difference is, however, more obscure. The inter molecular forces for fluorocarbons apparently have features wuich lead to anomalous behavior, at least from the point of view of solubility parameter theory [59]. Thus, theoretical calculations of the surface tension for the bare solid in the case of polytetrafluoroethylene would face a number of difficulties not encountered with paraffin crystals. 

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